1. Field of the Invention
The present invention relates to a rare earth magnet and a motor including the same, and more particularly, to a rare earth magnet used in motors for various electrical and electronic systems such as automobiles, computers, mobile phones, etc. and sound systems such as speakers, earphones, etc., and a motor including the same.
2. Discussion of Related Art
In general, there is a great demand for a neodymium (Nd)-iron (Fe)-boron (B)-based sintered permanent magnet as a rare earth magnet having a high energy product and a high coercive force. However, the sintered permanent magnet has a problem in that it has poor corrosion resistance since it includes the rare-earth element Nd and Fe, which are easily oxidizable, as major components.
To solve the above problems, methods of forming various protective layers on surfaces of the sintered permanent magnet have been proposed. Here, the protective layers are coated with a metal or a resin layer alone or in a combination thereof. In this case, various methods such as wet plating (e.g., electroplating, etc.), dry plating (e.g., sputtering, ion plating, vacuum deposition, etc.), dip coating, hot dip coating, electrodeposition coating, etc. have been used as a method of forming a film.
In the case of the electroplating, an electric current converges on an edge region of a product, and a relatively small amount of the electric current flows in a central region of the product, and thus the product may be formed so that a thickness of the coated edge region is 1.5 to 5 times a thickness of the coated central region. In this way, since the product is produced based on the thickness of the coated edge region to adjust the size of the product, the thickness of the coated central region becomes relatively thin, resulting in an increase in error rate of the products when commercialized. In particular, such a problem becomes more severe for pipe-type products having a narrow inner diameter.
Also, the crystals of an electroplated layer may grow in a direction perpendicular to a surface of a permanent magnet, and there may be pin holes in a plating layer due to huge crystal grains, resulting in degraded corrosion resistance.